Re: [PATCH v1 3/5] perf tools: Check if mem_events is supported for hybrid

[Jiri Olsa <jolsa@redhat.com>]

On Thu, May 20, 2021 at 03:00:38PM +0800, Jin Yao wrote:
> Check if the mem_events ('mem-loads' and 'mem-stores') exist
> in the sysfs path.
> 
> For Alderlake, the hybrid cpu pmu are "cpu_core" and "cpu_atom".
> Check the existing of following paths:
> /sys/devices/cpu_atom/events/mem-loads
> /sys/devices/cpu_atom/events/mem-stores
> /sys/devices/cpu_core/events/mem-loads
> /sys/devices/cpu_core/events/mem-stores
> 
> If the patch exists, the mem_event is supported.
> 
> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
> ---
>  tools/perf/util/mem-events.c | 43 +++++++++++++++++++++++++++++-------
>  1 file changed, 35 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
> index c736eaded06c..e8f6e745eaf0 100644
> --- a/tools/perf/util/mem-events.c
> +++ b/tools/perf/util/mem-events.c
> @@ -12,14 +12,16 @@
>  #include "mem-events.h"
>  #include "debug.h"
>  #include "symbol.h"
> +#include "pmu.h"
> +#include "pmu-hybrid.h"
>  
>  unsigned int perf_mem_events__loads_ldlat = 30;
>  
>  #define E(t, n, s) { .tag = t, .name = n, .sysfs_name = s }
>  
>  static struct perf_mem_event perf_mem_events[PERF_MEM_EVENTS__MAX] = {
> -	E("ldlat-loads",	"cpu/mem-loads,ldlat=%u/P",	"cpu/events/mem-loads"),
> -	E("ldlat-stores",	"cpu/mem-stores/P",		"cpu/events/mem-stores"),
> +	E("ldlat-loads",	"%s/mem-loads,ldlat=%u/P",	"%s/events/mem-loads"),
> +	E("ldlat-stores",	"%s/mem-stores/P",		"%s/events/mem-stores"),
>  	E(NULL,			NULL,				NULL),

so this was generic place, now it's x86 specific, I wonder we should
move it under arch/x86 to avoid confusion

>  };
>  #undef E
> @@ -100,6 +102,18 @@ int perf_mem_events__parse(const char *str)
>  	return -1;
>  }
>  
> +static bool perf_mem_events__supported(const char *mnt, char *sysfs_name)
> +{
> +	char path[PATH_MAX];
> +	struct stat st;
> +
> +	scnprintf(path, PATH_MAX, "%s/devices/%s", mnt, sysfs_name);
> +	if (!stat(path, &st))
> +		return true;
> +
> +	return false;

could be just 'return !stat(path, &st);' right?

> +}
> +
>  int perf_mem_events__init(void)
>  {
>  	const char *mnt = sysfs__mount();
> @@ -110,9 +124,10 @@ int perf_mem_events__init(void)
>  		return -ENOENT;
>  
>  	for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
> -		char path[PATH_MAX];
>  		struct perf_mem_event *e = perf_mem_events__ptr(j);
> -		struct stat st;
> +		struct perf_pmu *pmu;
> +		char sysfs_name[100];
> +		int unsupported = 0;
>  
>  		/*
>  		 * If the event entry isn't valid, skip initialization
> @@ -121,11 +136,23 @@ int perf_mem_events__init(void)
>  		if (!e->tag)
>  			continue;
>  
> -		scnprintf(path, PATH_MAX, "%s/devices/%s",
> -			  mnt, e->sysfs_name);
> +		if (!perf_pmu__has_hybrid()) {
> +			scnprintf(sysfs_name, sizeof(sysfs_name),
> +				  e->sysfs_name, "cpu");
> +			e->supported = perf_mem_events__supported(mnt, sysfs_name);
> +		} else {
> +			perf_pmu__for_each_hybrid_pmu(pmu) {
> +				scnprintf(sysfs_name, sizeof(sysfs_name),
> +					  e->sysfs_name, pmu->name);
> +				if (!perf_mem_events__supported(mnt, sysfs_name))
> +					unsupported++;
> +			}
> +
> +			e->supported = (unsupported == 0) ? true : false;

could you just do in the above loop:
			e->supported |= perf_mem_events__supported(mnt, sysfs_name);

jirka

> +		}
>  
> -		if (!stat(path, &st))
> -			e->supported = found = true;
> +		if (e->supported)
> +			found = true;
>  	}
>  
>  	return found ? 0 : -ENOENT;
> -- 
> 2.17.1
>